1. Field of the Invention
This invention relates to the field of motor vehicles. More specifically, the invention comprises a system and method for reducing the idle time of an internal combustion engine by allowing certain loads that are customarily carried by the engine to be selectively transferred to the vehicle's electrical system.
2. Description of the Related Art
Motor vehicles generally include two interlinked energy systems. These are: (1) the internal combustion engine that is used to propel the vehicle; and (2) the electrical system that is used to provide energy to electrical components such as lights, blower motors, and communication equipment. The electrical system generally includes an alternator and at least one storage battery. The alternator converts some of the mechanical energy produced by the internal combustion engine to electrical energy that is either used immediately or stored in the battery.
The inclusion of the storage battery allows certain electrical devices to remain active even when the internal combustion engine is not running. For example, the vehicle's radio and interior lights may be run for a substantial length of time (up to several hours) by drawing energy stored in the battery. For most vehicles, a fairly limited amount of storage capacity will suffice. This is true because the electrical systems are not used thr extended periods of time when the motor is not running. Most users enter a motor vehicle with the intention of driving somewhere. Thus, most prior art motor vehicles have only a limited capacity for operating the electrical systems when the internal combustion engine is not running.
The situation is quite different for service vehicles such as police patrol cars. A police patrol car includes significantly more electrical components than a typical motor vehicle. For example, a police cruiser includes a high-intensity light bar on its roof. In addition, a cruiser includes one or more two-way communication radios that are almost always switched on. The electrical energy consumed by these components is much greater than for a typical car.
In addition, many electrical components of a police cruiser are routinely in use while the car is stationary. For example, a police car parked at a vehicle accident scene typically runs its emergency lights, its radios, and an internal computer system.
An even more significant problem exists in warmer climates. Pace officers must often remain within a parked patrol car for extended periods of time (up to and including several hours). When high ambient temperatures are present, the patrol car becomes unbearably hot. The solution to this problem is to leave the internal combustion engine running so that the alternator can carry the electrical load and the mechanically-driven air conditioner compressor can drive the vehicle air conditioner.
Police patrol cars are configured to remain stationary with the engine at idle speed for several hours. Electrically-driven cooling fans force air over the vehicle's radiator so that it does not overheat. In addition, supplemental idle speed control systems may be provided to “kick up” the idle speed in order to provide sufficient charging current from the alternator and sufficient rotational speed for the air conditioner compressor.
While these systems function, they are not very efficient. A typical police patrol car sits at idle for several hours each day. This process wastes fuel and produces additional exhaust products. In addition, the prolonged idling of the internal combustion engine reduces the engine life available for its primary purpose—moving the vehicle. The use of an idling internal combustion engine is in fact quite inefficient for driving the moderate electrical load (via the alternator) and the moderate mechanical load (the air conditioning compressor).
The inefficiency results from the fact that an internal combustion engine having considerable capacity (around 300 horsepower, or 224 kW) is being used to drive a relatively small load (around 10 horsepower, or 22 kW). As those skilled in the art will know, internal combustion engines are inefficient when operating near the bottom of the range of available capacity.
It would therefore be preferable to provide a system which is able to carry the electrical and mechanical loads for a stationary service vehicle without the use of the internal combustion engine that drives the vehicle. The present invention provides such a solution.